1. Field of the Invention
The present invention relates to electrical connectors, and, in particular, to plugs and receptacles designed to reduce crosstalk between adjacent conductors of different transmission paths.
2. Description of the Related Art
Near-end crosstalk refers to unwanted signals induced in one transmission path due to signals that are transmitted over one or more other transmission paths appearing at the end nearest to where the transmitted signals are injected. Near-end crosstalk often occurs when the wires and/or other conductors that form the various transmission paths are in close proximity to one another. A classic example of near-end crosstalk is the signals induced during some voice transmissions that result in parties to one telephone call hearing the conversation of parties to another call. An example that would benefit from this invention is when high-speed data transmission is impaired due to coupling of unwanted signals from one path to another.
One type of plug used to terminate multi-wire cords is the 110-type patch cord plug, manufactured by Lucent Technologies, Inc., of Murray Hill, N.J. A 110 patch plug can be mated to the insulation displacement contacts (IDCs) of a 110-type connecting block, which is also manufactured by Lucent Technologies. One end of the 110 patch cord plug terminates permanently a multi-wire cordage; the other end mates removably to a 110-type connecting block. The 110 patch cord plug is often used in voice and data transmission applications. In such transmissions, each pair of conductors within a multi-wire cable, called the TIP conductor and the RING conductor, that carries balanced signals constitutes a single signal transmission path. A typical 8-wire cable can therefore support four different voice or data signal transmission paths.
A 110-type patch cord plug can have one or more pairs of conductors (typically 1, 2, 3, or 4 pairs). One end (i.e., the mating end) of each plug conductor has a blade contact to engage the split-beam contacts of a 110-type connecting block. The other end (i.e., the cable end) of each plug conductor has a split-beam contact to enable termination of the patch cord cordage conductors. The blade contacts are sequenced in a linear alternating fashion between TIP and RING conductors in order to be aligned with the split-beam contacts of the mating connecting block.
FIG. 1 shows perspective, top, and side views of the conductors of a prior art 110-type patch plug. FIG. 2 shows a schematic diagram of the cable and mating ends of a prior art 110-type patch plug. As shown in FIGS. 1-2, a 110 patch plug has up to four pairs of conductors, each pair (T.sub.i, R.sub.j) corresponding to a single balanced transmission path. Due to the proximity of the transmission paths within plugs (such as the 110 patch cord plug), signals in one transmission path can induce crosstalk in one or more adjacent transmission paths within the same plug. For example, signals in the transmission path transmitted through TIP contact T.sub.2 and RING contact R.sub.2 can induce crosstalk in the transmission path consisting of TIP contact T.sub.1 and RING contact R.sub.1, as well as in the transmission path consisting of TIP contact T.sub.3 and RING contact R.sub.3.
What is needed are plugs, such as patch cord plugs, and their accompanying receptacles, such as connecting blocks, that are designed to have low crosstalk between the transmission paths of multi-wire circuits. Previous attempts at reducing crosstalk have involved increasing the distance between transmission paths (i.e., from one pair of conductors to another) and/or decreasing the distance within each transmission path (i.e., between the two conductors of a single pair). Another approach is to introduce opposing crosstalk that is out of phase with the existing crosstalk. This is often done by designing a cross-over (i.e., a physical crossing of one conductor over another) in one or more pairs of conductors, while possibly leaving other pairs of conductors without a cross-over. The patch plug of FIG. 1 shows cross-over within each pair of conductors.